The blood-brain barrier (BBB) is a physical and metabolic barrier that separates the peripheral circulation from the central nervous system (CNS) and serves to regulate and protect the microenvironment of the brain. Disruption of the BBB occurs in a number of pathological conditions, including inflammatory regulated disorders, Alzheimer's disease, diabetes, multiple sclerosis, and ischemia/reperfusion. Hypoxia and reoxygenation correlate with changes in ischemia and reperfusion, are associated with various disease states which significantly influence the BBB, with subsequent effects in more sensitive neural tissue. Clarifying the extent and manner of BBB alterations induced by the hypoxia (H) and/or post-hypoxic reoxygenation (H/R), remains a considerable task. Examination of the regulation and activation of intracellular pathways, transcription factors, and tight junction proteins under such conditions is vital to understanding these BBB alterations. The overall goal of this submission is to determine the intracellular signaling mechanisms (protein kinase C and transcription factors) responsible for BBB structural and functional changes during hypoxia/post-hypoxic reoxygenation exposure. These studies will focus on the effects of H and H/R on the signaling molecule, protein kinase C, and the transcription factors, HIF1 and NFKappaB, and how these mediators contribute to BBB disruptions which lead to vasogenic brain edema, a major factor associated with ischemic stroke. Our hypothesis is that functional changes at the BBB occur due to alterations in the cytoarchitecture of the endothelial cell as a result of intracellular mechanisms/ mediators stimulated by hypoxia and/or post-hypoxic reoxvqenation insult. To investigate this hypothesis, our objectives and Specific Aims are to examine the effects of H and H/R insult on capillary endothelial cells of the BBB, by examining BBB permeability changes, tight junction/ cytoskeletal protein expression and localization, and changes in transcription factor expression/activation in conjunction with cellular signaling pathways/mechanisms (PKC). This study requires the use of multiple techniques and the integration of both in vitro (i.e., rat cerebral microvessel endothelial cells) and in vivo (i.e., Sprague-Dawley rat cerebral microvessel) models to allow us to differentiate and correlate cellular signaling pathways to functional and structural changes associated with BBB perturbation following H and H/R insult. Our goal is to gain a better understanding on the mechanisms involved in hypoxia associated with ischemic stroke at the BBB, leading to better treatment paradigms.